DE60031607T2 - Process for high quality ink-jet printing with aqueous ink on ordinary paper at high printing speeds - Google Patents

Description

background the invention

These This invention relates generally to liquid inkjet printers and in particular the use of slow-drying ink with high surface tension, which is dried in a manner to obtain a high image quality. Although not limited on this, the present invention provides for use in conjunction with acoustic ink printing has special advantages.

acoustic Ink printing is one maybe important technology for the direct mark. It compares preferably with conventional Inkjet systems for printing either on plain paper or on specialized recording media, while as such they offer significant benefits provides.

Inkjet printing systems for drops on request and for continuous stream have shown reliability issues because they are on nozzles leave with small ink ejection openings, which are easily clogged and which limit the life, if the size of the inkjet drops is reduced. Acoustic printing avoids the need for such nozzles, which makes it not just a bigger inner one reliability has as conventional Inkjet printing systems, but also with a greater variety of inks, including inks which are relative high viscosities and inks, which pigments or other particulate components contain. It was further found that acoustic printing a relatively precise one Positioning of individual printed pixels ("pixels") while it is providing allowed the size of this Picture elements during to adjust the operation, either by controlling the size of each Ink drops, which ejected or by regulating the number of ink drops which used to print the individual picture element Train image.

If an acoustic beam strikes a free surface (i.e., a transition Liquid / air) reaches a supply of liquid from below the radiation pressure which the beam is against surface of the stock, a sufficiently high level to individual drops of liquid release from the supply despite the restraining force of the surface tension. Focusing the beam on or near the surface of the stock intensifies the radiation pressure, which the same for a given Quantity of input power. The basic principles of acoustic ink printing are well known and the subject of several commonly issued US patents.

One particular advantage of the acoustic ink printing consists in the Ability, To produce drops that are much smaller in size as the opening, through which the drops are ejected. It was found that acoustic ink printing can produce drops, which one Magnitude smaller in size are as the one of the nozzle opening and significantly smaller than existing, conventional inkjet printing systems. This makes possible, that an acoustic ink pressure system previously unavailable, high resolution Images created because an important factor to achieve the high resolution in the filing of the smallest possible Stain exists on a recording medium.

at However, current printing practice is the current practice as well as conventional inkjet printing and for acoustic ink printing in the use of fast-penetrating inks (also known as fast-drying inks or low-ink inks Surface tension) for watery Inkjet printing. The fast-penetrating inks are those which generally into the fiber of the blank paper in less penetrate as three seconds, thereby allowing the ink quickly on the surface spread of the paper and also infiltrated into the paper.

One Advantage of using fast drying inks is in the context of color printers, to mixing between colors which would generally take place when slowly drying Inks which are also inks with high surface tension are known.

One Another advantage of using fast-drying inks for the Color printing is when you place the inks on the print media (e.g., paper such as blank paper) the first deposited ink will not tend to be on the surface, i. the same will already have been absorbed into the paper, if a second Color ink deposited on this spot or adjacent to it becomes.

Therefore, the second deposited ink will not run over the first ink. The rapidly penetrating ink soaks into the paper before the second color ink is ejected onto the same paper surface. Furthermore, the penetration of the first ink is fast enough to reduce lateral migration into adjacent pre-printed locations, thereby reducing intercolor mixing normally associated with conventional slow dry ink printing techniques would kick.

It However, there are some disadvantages to using fast drying Inks. In particular, by the penetration of the ink into the paper, is a proportion of the colorant or dye also in the paper transported. This results in a low optical density of the printed Material and also a stronger one Show through when the paper is out of the unprinted side is looked at. In particular, the greater colorant content reduces which is moved into the paper, the amount of colorant, which through the viewer is visible because the fibers are the reflection of the Block colorant.

existing, conventional Ink jet printing machines which use fast drying inks, usually reach an optical density of 1.2 to 1.3 when using blank paper. This is comparable to high quality xerography at 1.8 to 2.0 and photography of 2.1 to 2.3 optical density.

Of the Disadvantage for the back Show through is the impossibility of duplex printing. Because the use of fast-drying inks in many cases in particular, sucking the ink through the opposite one Side of the paper, two-sided printing would not be possible, there the ink, which shines through the opposite side destroy the second pressure would.

The Feature of rapid penetration / suction of fast-drying Inks in the paper causes additional slightly lateral suction depending on the surface topology of the paper. This causes a poor edge sharpness printed lines and text.

A high edge sharpness is desirable in any printer the typical goal being laser quality printing. Focus on color printer typically affect the quality of color reproduction and get less attention with the edge definition.

black Inkjet printers that achieve sharp edges on blank paper can are inherent slowly drying. This means that one side is still wet and will be smudable if it is spent when not significant amounts of drying time and / or thermally assisted drying to be provided. The acoustic ink printing is because of his ability to provide edge sharpness without frayed edges desirable, because it can apply such small drops, which one allow high dots per inch value.

At the Color printing is through the use of fast-drying inks diminishing the mixing between colors. Although fast drying Inks have a lower edge definition become the same still used in existing systems for color reproduction. at existing systems could a color printer is a slow-drying ink for monochrome black text and use graphics and fast-drying color inks for color reproduction. In this use, it is common that the slow drying of the black ink is a blending between colors when colored with the same colors Printing will be used or the same will require a significant drying time.

One essential aspect of printing is the removal of the liquid from the drops deposited on the recording medium. For example can the liquid from the ink and printed media by a number of methods be removed. A simple process is natural air drying, in which the liquid component evaporate the ink deposited on the medium without mechanical support what a natural Drying results. Another method is the to send printed substrate through a dryer to the liquid to evaporate. In some cases a special paper is used in which the liquid passes through a thin one Coating is absorbed with absorptive material which on the surface of the paper is deposited. Aspirate the printed medium is also known.

in the Case of natural Drying becomes nearly 100% of the liquid is absorbed into the paper and then naturally evaporated over a long period of time. The absorption and de-absorption of water in and out of the paper However, there are some undesirable ones Side effects, such as a long drying time, a strike through, Fringing at the edges of the printed image, paper blurring and paper waste. In the case of paper distortion relaxes the Absorption and the de-absorption of water the internal stresses of the paper, causing a paper warpage. exploitation is also a function of the per fluid area deposited Liquid. Lower printing on a paper has less potential for the Development of recovery due to the small amount of liquid. Increased printing on a paper has a greater potential for warping due to a higher Amount of liquid per unit area. Warp can also be done by heating of the paper resulting in a stress release.

DE-A-3642204 describes an ink jet printer. There are drops of ink Nozzles one Printhead ejected onto a substrate, around points on it to create. To smear the ink drops on different To avoid substrate materials, heats a drying device the substrate such that the heat for one certain time after the ejected ink drops on the Substrate have been stored, remains in the substrate. Therefore The drops of ink, which are a spherically swollen form according to the surface tension have dried in this state.

Summary the invention

It In particular, the object of the present invention is a liquid ink printer in terms of maintaining high image quality in applications to improve with high throughput. This goal is provided by a liquid printer according to claim 1 and a method for printing according to claim 2.

Short description the drawings

1A Fig. 10 is a cross-sectional view showing a fast-drying ink deposited on a paper surface;

1B FIG. 12 is a cross-sectional view showing a fast-drying ink on the paper surface of the 1A illustrated after a predetermined period of time;

2A FIG. 12 is a cross-sectional view illustrating a slow-drying ink after it has been deposited on a surface for a period of time identical to the fast-drying ink of FIG 1A is;

2 B FIG. 12 is a cross-sectional view illustrating the slow-drying ink of FIG 2A on a surface of a paper illustrates for an identical time as the fast drying ink 1B ;

3 Fig. 10 illustrates a printer architecture for an embodiment of the invention;

4 illustrates a second embodiment of the invention; and

5 illustrates a third embodiment of the invention.

INCOMING DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference hereinafter to the drawings and in this case, in particular to the 1A - 1B , a drop of fast drying ink (also known as low surface tension ink) 10 shown on the surface of a recording medium such as paper 12 was deposited, shown in cross-section. A fast-drying ink has certain properties, among which the characteristic of spreading on the surface of the paper and the rapid sucking or penetration into the fibers of the paper 12 such is that the same through the surface 14 of the paper 12 passes. This spreading involves lateral migration, which causes the ink to cover an undesirably larger area than the original perimeter 16 the deposited ink. The 1B shows the remaining colorant 10 ' fast-drying ink drop 10 of the 1A after it has reached a substantially dry state due to removal of the liquid in the drop. As can be seen, the size of the remaining color material 10 much larger than the original size of the drop on the paper. Furthermore, it is shown that the colorant 10 ' through the back 18 of the paper 12 is squat. This illustrates the ink bleed that occurs when using fast-drying inks that quickly wick or penetrate into the fibers of the paper.

With further reference to the 2A is a drop of slowly drying ink (alternatively referred to as high surface tension ink) 20 shown. The ink drop 20 has been on the paper 22 for the same amount of time as the ink drop 10 of the 1A on paper 22 found. As can be seen, the high surface tension of this ink causes the droplet to have larger angles to the paper surface than that of the drop 10 of the 1A , While a fast-drying ink such as in 1A usually has a penetration time of less than three seconds, a slow-drying ink will have a penetration time greater than three seconds. According to the teachings of the present invention, the ink drop becomes 20 actively dried in a quick-drying process to evaporate water from the drop, reducing the colorant 20 ' on the surface of the paper 22 , as in 2 B shown, lingers. Like in the 2 B illustrates, the colorant is substantially on the surface of the paper 22 arranged and has not, unlike the colorant of the 1B , essentially about its perimeter area 24 spread out. In other words, the small drops deposited on the paper are prevented from expanding, thereby maintaining the high resolution of the image.

Furthermore, the colorant is not in the interior of the paper 22 sucked. The advantages of it are that the optical density of the color for a viewer will be much larger than that of the colorant of the 1B because the colorant of the 2 B is not blocked by being held in the fibers of the paper. Because the size of the dried colorant is essentially of the same circumferential size of the drop 20 is, it is possible to produce a high edge sharpness, which when using in the 1A and 1B used printing method is unreachable. If another color is placed on the same or a different part of the paper, bleeding between the colors will be avoided since the first color has already dried. Because the colorant on the surface of the paper 22 is held, there is also no show through of the colorant on the back of the paper.

Therefore illustrate the 2A and 2 B the characteristics of the present invention which applies concepts contrary to those used in existing liquid ink printing processes. In particular, it is conventionally believed that in color printing it is best to use fast drying inks which are absorbed by the paper fibers to quickly dry the paper for the next application of ink. On the other hand, the present invention involves an opposite approach, which is to hold the ink drops on the surface of the paper and then to actively dry the ink drops by the application of heat during the printing process. This retains the ink drops in a small uniform manner, similar in size and shape to the original deposited drops, which in turn maintains the high image resolution.

The present invention includes further improvements compared existing systems. Since existing systems use the ink in the Allows fibers to penetrate, it is necessary to remove moisture from fibers. Especially These allow the moisture on the front surface of the Paper comes when it gets the moisture out of the back of the paper by back heating. This is an ineffective way to remove the moisture. The The present invention heats the ink drops by front heating the liquid essentially passes into the fibers of the paper. In the present invention less energy is needed because it is not necessary to dehumidify the fibers, i. the Dehydrate fibers and turn new fibers of free energy to create. Therefore, the front-side heating described below becomes preferable if an increase in the throughput of the Printing press desired becomes.

If For example, the machine has ten pages per minute to print only six seconds to print before the next sheet goes through, so that only six seconds available stand before it becomes necessary to bring out the sheet and place another paper sheet on top of the same. This does not allow passive drying but instead requires one active dry solution. The drying of the ink on the same side, to which the same was dropped, requires less energy when an ink of high surface tension is used because the ink is not essential in the paper fibers has arrived. Although the present invention has back drying be performed could, would one Such configuration slow down the printing process.

With reference to the 3 A first embodiment of a printing system that implements the concepts of the present invention is illustrated. The printing system 30 closes an input tray 32 one holding a supply of paper 34 ent holds. The paper is removed from the input tray 32 in engagement with the drum 36 emotional. The paper from the input 32 can through a preheating element 38 before the procedure with the drum 36 be preheated. In this embodiment, the drum has 36 of four inches diameter 60 ° C. It should be noted that drum with other properties can be used as well.

The printheads 40 . 42 . 44 and 46 are outside the drum 36 arranged in a manner wherein the drops ejected from the printheads are on the paper 34 be filed. Ink supply lines 48 convey ink from a supply source (not shown) to the printheads 40 - 46 , It will be a bent car 50 to carry the printheads 40 - 46 used. At operating distance to the drum 36 are the dryers (heaters) 52 and 54 arranged. In this embodiment, the printhead is 44 a magenta printhead, the printhead 42 a black printhead, the printhead 44 a yellow printhead and the printhead 46 a cyan print head. However, it should be appreciated that the present invention would work with a monocolor system such as a black system or a system with colors other than CMYK. The printer 30 is designed to produce 10 pages per minute. The printheads 40 - 46 are in two banks 40 - 42 and 44 - 46 around the drum 36 arranged around. In this version, the dryers 52 . 54 As a radiant heater, however, other types of drying equipment such as microwave, air, gas, reflective, conductive, or other drying sources may be used which could allow for rapid drying of the ink.

If the paper 34 by the circulating drum 36 is moved, the first color printhead comes into contact 40 Ink on the paper 34 off, which then turns on the dryer 32 moved past. The printhead prints 44 on the same, the neighboring or another paper place. Then the paper becomes 34 with the second paint on a second dryer 54 passed and dried substantially during the first drum rotation. During the second drum rotation, the third color print head 42 on the paper 34 Print and then the dryer 52 essentially dry this newly applied ink. This process is repeated when the fourth printhead 46 Color prints through the second dryer 54 is dried.

The Heat applied to the ink drops allows printing with one Color, substantially immediately followed by an active evaporation / drying step.

Furthermore, in this architecture, the amount of energy supplied to the dryer is determined according to the amount of ink that is currently passing through one of the printheads 40 to 46 was adjusted by calculating image data for this printhead. The control of the output of the dryer 52 and 54 is through the controller 56 carried out. This process optimizes the drying / evaporation of the ink on the paper and avoids under-drying (paper warping) or over-drying (paper scorching). Adjusting the amount of heat energy transferred to a surface of a print medium is known in the art. Once the printer has completed its second revolution, the printed paper will be in the output tray 57 stored.

4 Figure 11 is a plan view illustrating a second embodiment of the present invention which is constructed in conjunction with a planographic printing system 58 to work, which is a printhead assembly 60 which is constructed as a page wide field which extends substantially the full width of the recording medium such as paper 62 extends. The paper is held in a stationary position while the printhead assembly 60 is moved. The printhead assembly 60 closes the printheads 64 - 70 one. On the printhead assembly 60 become also the heaters 72 and 74 carried. During a first pass in the direction 76 sets one of the selected printheads 64 - 70 Ink drops off. The ink is a slow-drying (high surface tension) ink type. While this ink is being splashed onto the paper surface, the trailing dryer dries 72 the deposited ink. When run in the direction 78 will process with another printhead and use of the dryer 74 repeated. The dryers 72 and 74 The radiant heaters or other drying devices may be related to 3 be discussed.

The printhead 60 again moves in the direction 76 and then in the direction 78 causing the process of deposition of ink drops from the remaining printheads 68 and 70 if necessary, and drying the ink drops with the associated trailing heaters 72 and 74 suitably done. It should be noted that an essential aspect of this embodiment is that prior to depositing a subsequent high surface tension ink from one of the printheads 64 to 70 the heater elements 72 or 74 have dried the ink that has just been deposited substantially. In this way, the same advantages that are present in the above imple mentation are achieved. Although in this embodiment, the dryer 72 . 74 as to the printhead assembly 60 it should be appreciated that these may be on a separate follower assembly which allows them to dry the ink drops in the manner described above.

Furthermore, the printhead assembly becomes 60 through transmission lines 80 supplied with ink from an ink supply source (not shown). Furthermore, there is a controller 82 designed to be the same as the printhead assembly 60 can be supplied with the desired image data to be printed and also (or as a separate controller, not shown) may include a possibility to determine the amount of ink that will deposit an ink head on an image and thereby that for the heaters 72 and 74 appropriate energy level. This concept is equally applicable to the designs in the 3 and 5 applicable.

With reference to the 5 A third embodiment of the present invention is illustrated for use with a partial width field type printing device shown in a side view. In this embodiment, the recording medium becomes 92 through the printhead assembly 94 printed with a field of partial width, which the printheads 96 - 102 includes. On the printhead assembly 94 with a field of partial width become the heaters 104 and 106 worn as well. The print head field 94 moves in a pendulum motion across the directions 108 (pointing in the drawing sheet) and 110 (pointing out the drawing sheet). An example of the operation of this embodiment includes the use of ink from the printhead 102 and drying this ink substantially immediately thereafter through the heater 104 as the printhead transverses in the direction 108 emotional. When moving across in the direction 110 in which ink from the printhead 96 is discarded, this ink is there Raufhin essentially by the heater 106 dried. The further transverse movements along the paths 108 and 110 are by dropping the ink from the printhead 100 , dried by dryer 104 and depositing ink through the printhead 98 passing through the dryer 106 dried is completed in a suitable manner. Thereafter, the recording medium becomes a predetermined distance in the direction 112 moves to the printing process to the end of the recording medium 92 continue. Through the transmission lines 114 The printheads are supplied with RF power and the image to be displayed and the amount of heat control in response to the image are determined by the signals from the controller 116 provided.

Claims (2)

A liquid printer ( 30 ), in which liquid ink ( 20 ) in response to image data on a recording medium ( 34 ) is deposited within a print zone, the printer comprising: a liquid printhead ( 40 ), which is arranged to operate within the print zone to produce liquid ink ( 20 ) on the recording medium ( 34 while it is in the print zone, in response to image data; an ink ( 20 ) of high surface tension, which is used as liquid ink deposited on the recording medium ( 34 ) is filed; and a drying device ( 52 . 54 ), which in relation to the ink print head ( 40 ) is arranged to the ink ( 20 ) of high surface tension, which on a surface of the recording medium ( 34 ) is to dry before the ink ( 20 ) of high surface tension into the recording medium ( 34 ), characterized by means for detecting an amount of the ink ( 20 ) of high surface tension deposited on the recording medium ( 34 ) is filed; and a controller ( 56 ) for adjusting an amount of drying energy passing through the drying device ( 52 . 54 ) to the ink ( 20 ) of high surface tension depending on the detected amount. A method of printing using a liquid ink printing apparatus, the method comprising: depositing a first ink ( 20 ) of high surface tension on a recording medium ( 34 ); Drying the first ink ( 20 ) of high surface tension before the first high surface tension ink enters the recording medium ( 34 ) is absorbed; Depositing a second ink ( 20 ) of high surface tension on the recording medium after the first high surface tension ink is substantially dried; and drying the second ink ( 20 ) of high surface tension before the second ink ( 20 ) of high surface tension into the recording medium ( 34 ), characterized by detecting an amount of the first and / or second ink ( 20 ) of high surface tension deposited on the recording medium ( 34 ) is filed; and adjusting an amount of a drying energy ( 52 . 54 ) associated with the first and / or second ink ( 20 ) of high surface tension depending on the detected amount.